CTFE pow()

[Iain Buclaw via Digitalmars-d]

On 1 January 2015 at 18:40, H. S. Teoh via Digitalmars-d
<digitalmars-d at puremagic.com> wrote:
> On Fri, Jan 02, 2015 at 02:56:16AM +1000, Manu via Digitalmars-d wrote:
>> Does anyone know how to fix this? Can we please do so? It's been a
>> problem for like 5 years it seems.
>> It's a bit insane that we can't resolve any non-linear functions at
>> compile time.
>
> I've been waiting for this since like, forever. We even have a D code
> implementation of pow() already (thanks to Iain), which *should* have
> been CTFE-able, if it weren't for CTFE limitations that prohibit
> reinterpreting float values in binary, which is required for certain
> basic operations like isInfinite, isNaN, etc..
>
> So it seems that the blocker right now is CTFE, which, unfortunately, is
> not a pretty piece of code, and requires quite a bit of care to get it
> done right.
>

The fundamental structure is in place in Target. where the paintAsType
implementation encodes/decodes from a char buffer (and supports up to
512 bytes).  You can add support for painting a double as a ushort[4]
by adding a loop, decodeInteger(e, buffer), decodeInteger(e,
buffer+2), etc...

The second part (and more crucial) is adding the capability into CTFE.
Shouldn't be much work, but I've yet to get round to it.

See: https://github.com/D-Programming-Language/dmd/blob/master/src/target.c#L287


What I'd put higher up on my list of things to address are CTFE-able
unions though.

Iain.